The cost of premium communication services such as cellular telephone or packet data services tends to be a significant impediment to universal use of these services. As a result, service providers regularly introduce new price schedules, often referred to as tariff options or outlay schedules to make these services more attractive to a wider group of consumers. Typically, these series of price schedules represent a series of so-called "Pareto" improvements, a new tariff option being a Pareto improvement over an established set of tariff options if at least one person is better-off economically and no one is worse off as result.
An ideal tariff structure generally would compute service charges ex post, i.e., the most economic tariff option would be used based on the customer's actual use during a particular billing cycle so that the customer would be charged the lowest amount supported by any one of the possible tariff options. In practice, however, complex tariffs are normally used to compute service charges ex ante, i. e., the customer pre-selects a tariff option based on expected traffic pattern and lives with the result, even though other options were available that would have resulted in lower service charges had they been selected ex post. Once a particular tariff option is chosen ex ante, the customer has little insight into the charges accruing, and is therefore exposed to the risk of incurring excessive charges. In addition, an unauthorized user, e.g., an overly talkative child or a thief who steals a cellular telephone to make unauthorized calls, may incur excessive charges under a tariff option selected by the primary user in expectation of low usage.
Unfortunately, cellular subscribers typically are limited in their ability to determine their status with respect to the tariff structure of the systems to which they subscribe. Conventional cellular radiotelephones provide mechanisms for measuring duration of a present call, for measuring and storing duration of a last call, for measuring and storing cumulative call duration, and for measuring and storing cumulative on-time. However, these parameters typically are not readily usable by the operator of the phone for determining usage with an eye to minimizing usage charges.